Apparatus for electroplating metal strip



Feb. 29, 1944. 4 E. D. MARTIN APPARATUS FOR ELEGTROPLATING METAL STRIP- Filed Jan. 12, 1940 W e/260;": 4404/22 Qfd/ZZ/Z IIIIIHH I IH IHHU H HHIHHHH I I L step, passes over ITED sTATE APrAaA'rUs FOR, ELECTROPLATING METAL I s'rmr --Edwin D. Martin, Chicago, 111., assignorto Inland Steel Company, Chicago, 111., a corporation of Delaware Application January 12, 1940,- Serial o. 313,538

4 Claims.

My invention relates to improvements in apparatus for electroplating metal strip and the like and more particularly to novel means for electrically charging the strip as it passes through the electrolytic bath.

[It has been rather'common practice heret o. fore .to pass the strip alternately faround rolls adjacent the-bottom of the plating bath and rolls .above the bath and to electrically'charg'e one or more of the upper'rolls in order to charge the strip so that it serves as the cathode' With such a-construction, difllcultiesare encountered as an electrolytic action takes place between the sur-- face of each charged roll and the strip and the surface of the roll is plated with a coating of the plating metal. This coating builds up and mars the plated surface of the strip and also caus'es'trouble due to the increase in the diameter of roll. l

The principal object of my invention is to provide a simple and efficacious structure and arrangement which overcomes these diiiiculties. To this end, and generally speaking, I use insulated rolls and employ an electrically charged band which is suitably mounted in contact with the metal strip to charge the strip.

Other objects and advantages will become ap-f parent as this description progresses and by reference to the accompanying drawing wherein:

Fig. 1 is a. somewhat diagrammatic side view of an' apparatus embodying my invention; and- Fig. 2 is a cross sectional view through the upper part of the. apparatus, as on the line 2-2 I of Fig. 1. 4

Referring to the drawing, the metal strip 3, which is to be plated, may be drawn from a coil or reel-and thenas one step of a continuous- -operation prepared orcleaned for the. plating,

operation. 1 The strip is formed of the desired base metal, such, for example, as steel or copper,

.and may be of any desired width and length.

The strip, after being prepared forthe plating the first of the rolls l-which are mounted on brackets 5- fixed tothej opposite sides of the top of a tank B-containing the desired electrolytic bath 1, such, for example, as

one containing tin.

Suitably journaled near the bottom of the right hand roll 4 and through any subsequent finishing steps of the process and is finally wound on a reel or cut into sections, as may be desired. The strip may be pulled through the' tin, for example, are suitably suspended in the bath and between the vertical sides of the loops formed in the strip by passing it over the rolls 4, and 8. Squeegee pads or rolls I3, suitably mounted in spaced positions above the tank, serve to remove the excess electrolyte from the strip as it emerges from the bath.

"As already mentioned, it has-been heretofore one practice to form the upper rolls or their surfaces of conducting material, such as nickel or copper, for example, and to provide such rolls with electrical brushes connected to thenegative pole of a source of power in order to electrically tank are a'plurallty of rolls 8 in staggered-relation with -respect to the rolls 4. The rolls 4 and 8 are all insulated rollers, being formed of or for example, as rubber'or porcelain. Thestrip charge the metal strip as the cathode. As before stated, thisarrangement. has serious objections in that an electrolytic action takes place between conducting rolls and the strip with the result thatthe surface 'of such roll becomes plated and the strip is marred and the diameter of the roll is increased. I overcomethese. difllculties by insulating all of the upper rolls or by forming all of the upper rolls or their surfaces of insulating material and providing an elec-' trically charged metal band l4 which is maintainedin contact with the strip 3 to be plated, as now will be described.

Mounted on the top 'of the tank 6 is I5, ,each' side of which comprises a top bar l6, end legs ll bolted to the top of the tank, and an intermediate arm l8. Insulated rolls 20 are positioned between the rolls 4 and have their shaft extensions mounted in tensioning means in the legs l1 and arm l8. As somewhat diagrammatically shown, these ten'sioning means may comprise blocks 2| tensions are mounted, and opposing springs 22 on each side of the blocks which are slidable in slots in the legs "and arm l8. vMounted in suitable tensioning devices 23 in the right hand ends of the bars l6 of the. frame I5, is a similar ends of the bars I6. is a conducting roll 25, which i has its shaft extensions journaled in insulating covered with a suitable insulating material, such,

blocks'carried by the bars. Brushes 26, connected to the negative pole of the source of power shown diagrammatically at 26' engage the shaft extensions 25* of the roll 25. The positive a frame in which the shaft expole of the source of power is,connected to the anodes II. The endless band ll of conducting material, such as copper, around the rolls it and II, and as the rolls 20' are located betwemtherollslthebandisi'irmlypressed the portions oi the strip ensam the rolls It will be apparent that the electrical charge of the band is conducted directly and efllciently to and over large surfaces oi'the strip I. as it passes over the rolls 4, and thus the strip is properly charged to act as the cathode during the plating operation. It is also obvious that my invention overcomes the difliculties heretofore encountered. The rolls 4 being electrically insulated, do not become plated so their surfaces remain smooth and their diameters do not increase. There may be a tendency to plate the outer surface of the band but this is not at all serious because of the large area of the band and the ease with which the coating may be removed without interfering with or interrupting the plating operation of the strip. The 'band ll, being in engagement with the strip as it passes over the rolls 4, also aids in synchronizing and equalizing the feed oi! the loops of the strip through the electrolyte. The inside 01' the band it, which engages the rolls 20, 24. and 25, remains substantially dry so that there is practically no electrolytic action between the band and these rolls. v

I have illustrated one form oi embodiment of my invention, but it. will be understood that changes in detail and arrangement or parts may be resorted to without departing from my invention as defined by the claims that iollow. For example, the number of rolls 4 may be varied or the band may be arranged to coact with less than all of therolls 4. Further, one or more of therolls carried by the frame it may be positively driven, in order that the band It may aid in advancing or feeding the strip l-through the apparatus.

I claim:

1. In an apparatus for electroplating a metal strip bypassing the strip through an electrolytic bath, the combination with a plurality of insulated rolls adjacent the bottom oi the bath and a plurality of insulated upper rolls. above the 50 lated rolls, the band engaging the upper surface" bath, the strip alternately passing underneath and about the lowerrolls and over and about the upper rolls, of a plurality'ot band-engaging rolls,

some or which are between said insulated upper rollsand one or which is electrically charged,

and a flexible conducting band'passing around said band-engaging rolls, the band engaging the strip as it over said upper insulated rolls to electrically charge said strip.

s 2. In an apparatus for electroplating a metal strip by passing the strip through an electrolytic bath, the combination with a-pluraiity o! insulated rolls-adjacent the bottom of the bath and a plurality of insulated upper rolls above the i0 bath, the strip alternately g underneath and about the lower rolls and over and about the upper rolls, of a plurality of band- 8 8 8 rolls some of which are between said insulated upper rolls and one or which is electrically charged, a

is flexible conducting band passing around said band-engaging rolls, the band engaging the strip as it passes over said upper insulated rolls to electrically charge said strip, and tnsioning means for resiliently maintaining the band .20 against the strip.

3: In an apparatus for electroplating a metal strip by passing the strip through an electrolytic bath, the combination with a plurality of insulated upper rolls, the strip passing over and 25 about the upper rolls above said bath with portions of said strip extending down between said upper rolls and through said bath, of a plurality of band-engaging rolls above said bath at least one of which extends between adjacent upper in- 30 sulated rolls and at least one 01' which is con- .ducting and electrically charged, and a flexible conducting band passing around said band-engaging rolls and above said upper insulated rolls.

the band engaging the upper surface of said 36 strip as it passes over said upper insulated rolls.

to electrically charge said strip.

4. In an apparatus for electroplating a metal strip by passing the strip through an electrolytic bath, the combination with a plurality oi"=insu-- o lated upper rolls above the bath, the strippassing over and about the upper rolls with portions 7 of said strip extending down between said upper. rolls and through said bath, oi a plurality oi band-engaging rolls above said bathat least.

45 some of which are positioned between adjacent upper insulated rolls and at least one of which is conductive and electrically charged, and a flexible conducting band passing around said band-engaging rolls and above said upper insuof said strip' as it passes over said upper insulated rolls to electrically charge said strip.

'sznwm n. MARTIN. 

